This invention relates generally to the testing of cathode ray tubes (CRT) and particularly to a system for applying a high voltage source to such a tube through a cable which constitutes a high capacitive load.
One of the final stages in the production of color television picture tubes is that of testing the tube for focus and convergence using a high voltage drive. The convergence test is needed to assure that the electron beams from the three electron guns converge at the proper point with respect to the shadow mask so that the color purity is acceptable. The focus test is needed to assure that the electron beams are properly focused. Additionally, typically color television tubes defocus if driven by too high a voltage. Thus, a high voltage drive test is used to measure the capability of the tube to stay focused during the presence of a high drive voltage.
Typically, during test, the drive voltage is applied to the tube under test from a remote test station. Accordingly, a long coaxial cable is used to couple the tube to the test station. Such cables have high capacitance making it difficult to apply a high voltage, narrow time pulse to the tubes.
The instant invention fulfills this requirement by the provision of a system for applying a high voltage, narrow time pulse to a cathode ray tube through a high capacitive load, such as a coaxial cable.